March 3, 2012

[Update 8th Aug 2012: This is an older method of setting up the monitor kept for historic reasons. In the newer version of KDE the process is a lot simpler, please refer to this post for the updated steps – Suramya.

Recently I went ahead and bought two new Dell 20″ monitors for my home system as I had gotten used to working with two monitors at work and wanted the same experience at home as well. The problem started because initially I tried installing another graphics card and hooking up the second monitor to that card using VGA. For some reason maybe because I was to tired and wasn’t thinking clearly, I couldn’t get both the cards to work at the same time. I would get one or the other but not both. To make things even more fun, the monitors are 16:9 aspect ratio and when I used the Opensource driver the only resolution with that aspect ratio I would get was 1600×900 which was too small and the fonts looked kind of jagged at that resolution.

Since I was going to be out of town and was planning on switching to DVI cables anyways I left the system like that (after spending a bit of time experimenting) and left. Once I got back I ordered DVI cables and finally managed to get the dual monitor setup working after spending about an hour one the issue. Below is the sequence I followed to get stuff to work (documenting this so that if I ever have to do this again I have a record of what I did):

Removed the second video card to reduce complexity. Might add it back later if required, or if I want to hook my old monitor as a third display.

Connected both monitors to the onboard ATI Radeon HD 4250 card, one over DVI and the second using VGA

Removed the Proprietary ATI and nVidia drivers (both installed in my previous attempts to get this working). Instructions here

Once the driver was installed I restarted X once again and got both monitors working, but the second monitor’s display was a clone of the first one which is not what I wanted so I had to do some more digging and finally managed to fix that using the following steps:

Open a terminal/Command Prompt

Disable access control so that clients can connect from any host by issuing the following command as a regular user

xhost +

This is required so that we can start a GUI command from a root shell. If we don’t do this you will get an error similar to the following in the next step:

There is a bug in the display manager that prevents it from saving any changes if the xorg.conf file exists, to fix:

Run the following command as root:

mv /etc/X11/xorg.conf /etc/X11/xorg.conf_original

Click ‘Apply’ in the Catalyst Control Center

Restart X

That’s it. Once I did all that, my dual monitor setup started working without issues. Well… mostly. For some reason my desktop effects have stopped working (Transparent/Translucent windows etc) but I am not going to worry about it for now. That’s a battle for another day, maybe over the weekend.

Please note, that setting up Dual monitors usually is not this complicated in Linux. When I hooked up my TV to this same system I didn’t have to make any changes to get it to work. In this case since I was fiddling around I had to fist fix the mess I made before I was able to get this to work properly.

For those of you who are interested, the final xorg.conf that the above steps created is listed below:

One Response to " Configuring Dual monitors in Debian "

[…] but this time it was fairly simple. I thought that I would follow the same steps I had the last time I installed the monitor so I started by installing the fglrx driver but the latest version of the driver no longer supports […]